GH-49890: [Dev] Group files under component comment headers in .github/CODEOWNERS (#49891)

### Rationale for this change

Based on the feedback shared by @ kou in #49811 (comment), we should consider grouping files under component comment headers in `.github/CODEOWNERS` to improve readability.

We should also add `@ kevingurney` and `@ sgilmore10` as `CODEOWNERS` for the MATLAB-related CI file `.github/workflows/matlab.yml`.

### Component(s)

Developer Tools

### What changes are included in this PR?

1. Group files under component comment headers in `.github/CODEOWNERS` file.
2. Add `@ kevingurney` and `@ sgilmore10` as `CODEOWNERS` for file `.github/workflows/matlab.yml`.

### Are these changes tested?

N/A.

### Are there any user-facing changes?

No.

### Notes

1.  Thank you @ sgilmore10 for your help with this pull request!
* GitHub Issue: #49890

Lead-authored-by: Kevin Gurney <kgurney@mathworks.com>
Co-authored-by: Kevin Gurney <kevin.p.gurney@gmail.com>
Co-authored-by: Sarah Gilmore <sgilmore@mathworks.com>
Co-authored-by: Sutou Kouhei <kou@cozmixng.org>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

Author: 3 people

.github/CODEOWNERS

@@ -25,21 +25,6 @@
 # Arrow Format
 # /format/
 
-## Components
-/c_glib/ @kou
-# /cpp/
-/cpp/src/arrow/acero @westonpace
-/cpp/src/arrow/adapters/orc @wgtmac
-/cpp/src/arrow/engine @westonpace
-/cpp/src/arrow/flight/ @lidavidm
-/cpp/src/parquet @wgtmac
-/matlab/ @kevingurney @kou @sgilmore10
-/python/ @AlenkaF @raulcd @rok
-/python/pyarrow/_flight.pyx @lidavidm
-/python/pyarrow/**/*gandiva* @wjones127
-/r/ @jonkeane @thisisnic
-/ruby/ @kou
-
 # Docs
 # /docs/
 # *.md
@@ -53,16 +38,41 @@
 .pre-commit-config.yaml @raulcd
 # .git*
 
-# release scripts, archery etc.
+# Release scripts, archery etc.
 /ci/ @assignUser @jonkeane @kou @raulcd
 /dev/ @assignUser @jonkeane @kou @raulcd
 .dockerignore @raulcd
 .env @assignUser @jonkeane @kou @raulcd
 compose.yaml @assignUser @jonkeane @kou @raulcd
 
-# R specific packaging tooling
+# Components
+
+## C GLib
+/c_glib/ @kou
+
+## C++
+/cpp/src/arrow/acero @westonpace
+/cpp/src/arrow/adapters/orc @wgtmac
+/cpp/src/arrow/engine @westonpace
+/cpp/src/arrow/flight/ @lidavidm
+/cpp/src/parquet @wgtmac
+
+## MATLAB
+/.github/workflows/matlab.yml @kevingurney @sgilmore10
+/matlab/ @kevingurney @kou @sgilmore10
+
+## Python
+/python/ @AlenkaF @raulcd @rok
+/python/pyarrow/_flight.pyx @lidavidm
+/python/pyarrow/**/*gandiva* @wjones127
+
+## R
+/r/ @jonkeane @thisisnic
 /r/configure* @assignUser
 /r/Makefile @assignUser
 /r/PACKAGING.md @assignUser
 /r/tools/ @assignUser
 /r/.Rbuildignore @assignUser
+
+## Ruby
+/ruby/ @kou